I have a Linux server running kernel 2.6.18.

The main hard drive began to fail the other day so we had a new drive put in, reformatted and reinstalled the system. There was a backup slave drive in the system that we just left alone.

After getting everything reinstalled, I went to mount the backup drive to /backup. It mounted just fine, but when I create files on the backup drive, they show up on the main drive under / !!?!?

I seriously had a hard time figuring out what to title this because it's such a weird problem.

Update: I just realized that the slave drive in question is also bootable. I had that taken out and now the system won't let them log in at the console. Any ideas?

That's fairly odd. I looked at your ticket history to see if I could login and spot the issue, however I don't see an open ticket. Can you PM me the ticket number so I can take a look?

What did mount indicate and what does your fstab look like?